1. Field of the Invention
This invention relates to a system for restraining the body of an occupant in a vehicle to reduce the extent and severity of injuries during a crash. More specifically, the invention relates to a seat belt restraint system which incorporates an inflatable tubular section in the torso section of the belt. The inflatable tubular section can be made of a woven or braided tube of continuous high-strength fibers or can alternatively be made from an extruded net or from a woven net. The restraint system reduces the extent and severity of both primary and secondary injuries to vehicle occupants.
2. Background of the Invention
Conventional seat belts are designed to protect the occupants of vehicles such as automobiles, trucks, vans, airplanes and helicopters from primary injuries during an accident. Primary injuries are injuries caused by the initial impact of the occupants against the interior of the vehicle. However, the protection provided by conventional seat belts against primary injuries may sometimes be inadequate. For example, slack in the seat belts may lead to unnecessarily serious primary injuries. In side impacts conventional belts do not provide occupant head protection on the struck side of the vehicle. Moreover, the seat belts themselves may often be responsible for secondary injuries, since the load from the seat belts is distributed only over small areas of the occupant""s body. However, some prior art belts have tried to lessen primary injuries by incorporating an inflating mechanism into the seat belt restraint.
For example, U.S. Pat. No. 5,282,648, which is incorporated by reference herein, discloses an inflatable body and head restraint system, wherein inflatable bladders are attached to the shoulder straps of a harness restraint. The bladders are stowed partially underneath and partially on top of harness straps. This configuration provides stability and prevents the bladders from rolling out of position during inflation. During a crash, the bladders inflate to protect the upper body, primarily the head and neck of the occupant.
Additionally, U.S. Pat. Nos. 3,948,541 and 3,905,615 to Schulman disclose another inflatable body and head restraint system, wherein a bladder is securely affixed to shoulder straps and a lap belt. The bladder has chin, chest, and pelvic bags. Upon impact, the bladder automatically inflates to cushion the pelvic areas and to prevent forward rotation of the head. However, upon inflation the bladder tends to roll out from its position under the shoulder straps. Also, because the bladders are constricted by the harness, portions of the bladder are subjected to high pressures, which can lead to splitting of the bladder.
Simple inflatable body restraints are also disclosed in U.S. Pat. Nos. 3,682,498 and 4,348,037 to W. Rutzki and B. Law et al, respectively. These patents disclose inflatable protective devices that are located in or under the seat harnesses to which they are attached. These inflatable body restraints are subject to roll-out and seam or web splitting problems.
In yet another prior art seat belt disclosed in, U.S. Pat. Nos. 3,841,654 and 5 3,970,329 both to Lewis, a vehicle seat system which comprises a seat belt having an inflatable section is shown. When a collision is detected, the inflatable section is inflated to protect the person wearing the seat belt.
The prior art inflatable seat belt structures, such as those identified above, generally use a unitary inflatable section made from a tightly woven material, such as 420 denier nylon, which is conventional air bag material. When deployed, the inflatable section will contract in length somewhat because the inflation pressure causes it to go from a flat, generally 2-dimensional shape to a 3-dimensional cylindrical shape. However, only the ends of the inflatable section contract as they fill and assume a hemispherical shape. This causes only the ends of the inflatable section to shorten, thus shortening the overall length of the inflatable section. The fibers of the material do not change their orientation: the two sets of fibers in the material remain roughly perpendicular to each other throughout the inflation process.
In the case of the typical inflatable seat belt made of conventional air bag material as described above, the maximum theoretical amount that the inflatable structure contracts upon inflation, in an unconstrained condition prior to being loaded by the occupant, is based only on the width of the flat material. If inflation results in a relatively small cylindrical diameter then a relatively small contraction, or shortening, of the length of the seat belt will occur. The calculation for determining the amount of contraction that will occur with conventional air bag material upon inflation and in an unconstrained condition is as follows:
Lfxe2x88x92Li=Xxe2x80x83xe2x80x83(1)
where:
X is the amount of contraction
Lf is the length of flat, uninflated, material
Li is the length of unconstrained inflated material, and
Li=Lfxe2x88x92(Dfxe2x88x92Di)xe2x80x83xe2x80x83(2)
Di=2/xcfx80(Df)xe2x80x83xe2x80x83(3)
Lfxe2x88x92Li=Df(1xe2x88x922/xcfx80)xe2x80x83xe2x80x83(4)
where:
Df is the width (flat diameter) of flat, uninflated, material
Di is the diameter of unconstrained inflated material.
As seen in equation (4), the length reduction depends solely on the uninflated width (flat diameter) of the material.
For example, an inflatable structure having a flat diameter of 20 cm and a flat length of 100 cm has a maximum achievable contraction of 7.3 cm or roughly 7% in the absence of any load. In an actual application, with the belt under tension, the contraction would be much less, e.g., about 3%. This degree of contraction would provide restraint that is only slightly greater, and, thus, only slightly more protective than a conventional seat belt.
The construction disclosed in U.S. Pat. No. 3,888,503 to Hamilton comprises an inflatable restraining band having a series of sections, some of which are inflatable to a greater degree than others interconnecting them. In the Hamilton design, contraction occurs upon inflation only at each end of each section, and because the sections are of variable inflatable size, the amount of contraction varies along the structure. By not allowing full expansion of interconnecting portions or sections of the inflatable band more hemispherical xe2x80x9cendsxe2x80x9d occur thus the overall band is foreshortened to a greater extent than otherwise on expansion, which causes greater tensioning of the band against the occupant restrained.
Hamilton provides greater protection than the conventional inflatable seat belt in terms of the provision of greater restraint and hence improves upon a conventional inflatable seat belt. However, the restraint that results from Hamilton""s patent is still significantly less than the restraint provided by the present invention.
None of the patents described above provide the important advantage of the significant contraction which occurs in the present invention as the inflatable structure expands upon inflation.
The present invention is a seat restraint system having an inflatable structure in the torso section of the system, connected to a gas generator and crash sensor, that shortens greatly as it inflates. The invention is intended to replace conventional automotive seat belts. It can also be used in other types of vehicles and moving structures, such as trucks, vans, airplanes, railroad trains, elevators and helicopters.
The inflatable structure is a key component of the present invention. The inflatable structure must have the following characteristics: (1) it must contract in length substantially as it is inflatedxe2x80x94the decrease in length of the inflated portion of the torso belt (measured when the torso belt is not under tension) must be at least 15%, and should preferably be 20% to 40%; (2) the area of the cross-section of the structure should increase substantially as the tube is inflatedxe2x80x94the increase should be at least 50%, preferably 50% to 100%; (3) it must remain at a relative pressure sufficient to maintain a tensile force on the torso belt of 100 lbs (at xcx9c1 g torso mass) for at least five seconds, and preferably at least 7 seconds; (4) the reduction in the length of the structure is the direct result of the inflation of the structure, which also results in an increase in the cross-sectional area of the structure. For example, an inflatable structure which is 91 cm long and has a diameter of 12 cm prior to inflation, reduces its length by about 28 cm and increases its diameter to 17 cm when the structure is inflated (not under tension).
In a first preferred embodiment of the present invention, the inflatable structure is a tubular structure that comprises a braided tube of continuous high-strength fibers (instead of the conventional material used for air bags). The fibers of the braided tube of the present invention form spirals and change their orientation upon inflation. Prior to inflation, the spirals are stretched-out longitudinally and the tubular restraint has a relatively small diameter, as shown in FIG. 2a. Subsequent to inflation, the spirals are closer together longitudinally and form a relatively large tubular diameter, as shown in FIG. 2b. That is, upon inflation, the braided tube significantly increases its diameter and significantly decreases its length. This contraction occurs because when the tube is inflated, the fibers seek an orientation that allows a lower resultant stress and hence a larger volume within the tube. In order to provide superior gas retention, braided tube preferably contains an inner bladder 222, as shown in FIG. 2c. 
In the uninflated state, the braided tube in combination with the conventional seat belt assumes a flat woven belt configuration and acts as a conventional seat belt system and holds the occupant in the seat. However, as the braided tube inflates, the decreasing tube length acts as a pretensioning device first by drawing any slack out of the seat belt system and second by pre-loading the occupant. The shortened length of the braided tube helps greatly to further restrict subsequent occupant motion.
The inflated braided tube additionally provides a much larger restraint surface area for the occupant""s body, which helps to distribute belt load forces. When the inflated braided tube is loaded by the occupant""s body, it flattens slightly. This flattening increases the contact area between the body and the braided tube, thus further reducing the stress or load concentration on the occupant. In a side impact the inflated section provides occupant head protection.
The inflatable braided tube is connected to a gas generator which is in turn connected to a crash sensor. When the crash sensor detects an impact above a predetermined threshold, it sends a signal to the gas generator. The gas generator is ignited, and generating inflating gas that inflates the braided tube. The gas generator can be integrated within the seat back or base, in the buckle assembly of the belt, or in the trunk of the vehicle, for sound damping purposes and/or other practical considerations.
In a second preferred embodiment of the present invention, the inflatable structure comprises an extruded net. An extruded net is likely to be less expensive to manufacture than a braided tube. It can also be manufactured with a more open weave than the braided tube, which could result in greater contraction. FIGS. 4a and 4b are schematic diagrams of an extruded net structure before and after inflation, respectively. The dimensions of FIGS. 4a and 4b show how, as the extruded net is inflated, it contracts in length as it expands in diameter. The extruded net differs from the braid because the intersecting fibers are joined at the intersections. When the extruded net is inflated, the joints deform such that the longitudinal angle of intersection of the fibers increases dramatically, as shown in FIG. 4b. The minimum longitudinal angle prior to inflation is about 5xc2x0. Typically, the longitudinal angle prior to inflation is about 10xc2x0-15xc2x0 and typically increases upon inflation to 90xc2x0-110xc2x0. The maximum longitudinal angle after inflation can be as high as 150xc2x0. This results in the desired inflatable structure, i.e., a structure which contracts substantially in length as it is inflated and the cross-section increases.
An alternative second preferred embodiment uses a modified extruded net, in which the intersections of the fibers are strengthened with nodes, as shown in FIGS. 5a and 5b. Typical materials that could be used to fabricate the modified extruded net include nylon and polyester fibers. The tensile strength of the net at the nodes should be equal to the tensile strength of the fibers.
A third preferred embodiment uses a woven net, as shown in FIGS. 6a and 6b. The woven net is similar to the extruded net, but the joints are woven together instead of being joined together. The joints are reoriented as the inflatable structure is expanded, as shown in FIG. 6b. Typical materials that could be used to fabricate the woven net include nylon, polyester and aramid fibers.
A fourth preferred embodiment, shown in FIG. 2d, uses a protective sheath 223 fabricated from woven fabric, e.g. nylon or polyester fabric, in addition to the braided tube and bladder. The sheath has the appearance and texture of a conventional seat belt.
The present invention may be implemented in the rear seat of an automobile by routing the inflatable section of the torso belt through a constraint at the top of the rear seat and down the back of the rear seat, essentially similar to the front seat installation shown in FIGS. 1a-1e. However, in an alternative embodiment of the present invention, the gas generator is installed behind the rear seat, as, for example, shown in FIG. 7a, and the inflatable section of the torso belt extends across the rear shelf of the vehicle towards the trunk. In the alternative embodiment shown in FIGS. 7a-7b, the inflatable section of the torso belt is shown as connected to a hose which is connected to a rigid pipe. The rigid pipe is connected to a gas generator, such that the pipe can rotate around the gas generator, without blocking in any way the fluid connection from the gas generator to the rigid pipe, or from the rigid pipe to the hose. The rigid pipe is biased towards the horizontal position.
FIGS. 8a-8c show an embodiment of the present invention for rear seat installation that is similar to that of FIGS. 7a-7b, but uses a hose retractor instead of a rigid pipe. In this embodiment, 800 is flexible, and tension is kept on the inflatable structure through the use of torsion 801 and rollers 802.
FIG. 9 is a schematic diagram of another embodiment of the present invention, for rear seat installation. This embodiment is similar to the embodiment shown in FIGS. 1a-1e, but uses the space between the seat back and the front trunk wall. The hose is bent into a U shape or J shape, as shown in FIG. 9, and held in place by a channel.
FIG. 10 is yet another embodiment of the present invention in which the inflatable torso belt is top-filled via a torso belt upper anchor arm that is pivotally mounted to the side of a seat back. In a preferred implementation of this particular embodiment, the anchor arm replaces a torso belt retractor and an associated D-ring, and functions as a torso belt height adjuster.
The primary object of the present invention is to prevent or reduce the severity of primary and secondary injuries suffered by a vehicle occupant in the event of a crash, by pretensioning the restraint system, further restricting the motion of the occupant""s body, by distributing the restraint forces over a larger surface area, and to provide side impact head protection.
Eight crash tests simulating four equivalent frontal and four equivalent side impacts were conducted to compare the restraining capability of the present invention to a conventional three-point seat belt, and to two prior art air belt systems. The first air belt was inflated to a relative peak inflation pressure of approximately 1 bar, and the second air belt was inflated to a relative peak inflation pressure of approximately 3 bars. The results of these tests are listed in Table 1. As shown by Table 1, the first air belt shows essentially no improvement over the conventional three-point seat belt. The second air belt shows some improvement compared to a conventional three-point seat belt, i.e., head displacement was reduced by six inches in the forward crash simulation and by 2.5 inches in the side impact simulation. Head rotation, a possible indicator of neck injuries, was also reduced. However, the restraint system manufactured according to the present invention, inflated to a peak inflated pressure of approximately 2 bars, produced the greatest improvements in occupant kinematics: head displacement was reduced by 15.5 inches (from 20.5 inches to 5.0 inches) in the forward direction) and by 8 inches (from 23 inches to 15 inches) in the lateral direction. The superior performance of the present invention is due to its ability to reduce its overall length to a greater extent than prior art restraints.
Accordingly, it is an object of the present invention to provide a protective seat belt system that inflates on impact to protect the occupant of a vehicle.
It is another object of the present invention to provide a protective apparatus that restricts occupant motion during a crash.
It is another object of the present invention to provide an inflatable braided tube member that can greatly shorten (by 20% to 40%) as it inflates to remove slack and pretension the restraint system.
It is another object of the present invention to provide an inflatable braided tube that distributes crash loads over larger occupant surface area, thus minimizing pain and potential injury.
It is another object of the present invention to provide an inflatable braided tube that is not subject to roping, roll-out or seam splitting problems.
It is another objective of the present invention to provide an inflatable braided tube that protects the head in side impacts.
It is another object of the present invention to provide a top-filled inflatable tube.
It is another object of the present invention to provide a top-filled inflatable tube which does not require a flexible fill hose which might need to continuously flex, bend or stroke during normal belt use.
It is another object of the present invention to provide a rotatable upper anchor arm for a top-filled inflatable tube that operates as a height adjustable upper anchor point for an inflatable torso belt.
These and other objects of the present invention are described in greater detail in the detailed description and the appended drawings.